In a traditional commercial mobile communications network, a user of a user equipment needs to perform scheduling and signal transfer using a network server, such as a base station, to establish a connection with a user of another user equipment. During an evolution process of the mobile communications network, for some network environments, such as a public security network and a location-based social network, a design requirement of device to device proximity service (D2D ProSe) is proposed. D2D ProSe supports direct communication between user equipments, that is, communication between user equipments directly occurs between related user equipments, and a third-party node does not participate in data communication between a source and a sink. D2D ProSe can meet a communication requirement of the public security network and the social network.
In D2D ProSe, a communication connection can be directly established between user equipments for communication, not requiring scheduling, transfer, and control of a base station. Therefore, D2D ProSe lacks control on direct communication between the user equipments. If a direct communication service is performed between user equipments not meeting sufficient communication conditions, quality of the direct communication is relatively poor.